Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at bfa.e(SourceFile:237)
	at bfl.a(SourceFile:1343)
	at bfe.a(SourceFile:810)

---- Minecraft Crash Report ----
// Why is it breaking :(

Time: 20/09/13 9:53 PM
Description: Unexpected error

java.lang.ArrayIndexOutOfBoundsException: 0
	at bfa.e(SourceFile:237)
	at bfl.a(SourceFile:1343)
	at bfe.a(SourceFile:810)
	at bfe.b(SourceFile:695)
	at atv.S(SourceFile:686)
	at atv.d(SourceFile:619)
	at net.minecraft.client.main.Main.main(SourceFile:101)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at bfa.e(SourceFile:237)
	at bfl.a(SourceFile:1343)
	at bfe.a(SourceFile:810)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bdi['RachelTiger'/43, l='MpServer', x=-1248.62, y=6.76, z=-54.97]]
	Chunk stats: MultiplayerChunkCache: 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-1259,4,-52), Chunk: (at 5,0,12 in -79,-4; contains blocks -1264,0,-64 to -1249,255,-49), Region: (-3,-1; contains chunks -96,-32 to -65,-1, blocks -1536,0,-512 to -1025,255,-1)
	Level time: 73405 game time, 105187 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 18 total; [ts['Slime'/1023798, l='MpServer', x=-1226.31, y=4.00, z=-41.87], ts['Slime'/1029580, l='MpServer', x=-1199.69, y=4.33, z=-39.82], ts['Slime'/1040063, l='MpServer', x=-1220.31, y=5.01, z=-57.13], ry['Pig'/34, l='MpServer', x=-1192.16, y=4.00, z=-41.31], ry['Pig'/35, l='MpServer', x=-1183.78, y=4.00, z=-56.72], rs['Horse'/32, l='MpServer', x=-1184.50, y=4.00, z=-119.22], rr['Cow'/33, l='MpServer', x=-1185.47, y=4.00, z=-120.75], rs['Horse'/38, l='MpServer', x=-1182.72, y=4.00, z=-125.25], rs['Horse'/39, l='MpServer', x=-1179.34, y=4.00, z=-115.84], ry['Pig'/36, l='MpServer', x=-1182.53, y=4.00, z=-57.06], ry['Pig'/37, l='MpServer', x=-1179.81, y=4.00, z=-39.09], rs['Horse'/40, l='MpServer', x=-1178.59, y=4.00, z=-120.50], ts['Slime'/1017119, l='MpServer', x=-1197.35, y=5.01, z=-91.57], bdi['RachelTiger'/43, l='MpServer', x=-1071.31, y=-252.34, z=-224.30], bdi['RachelTiger'/43, l='MpServer', x=-1248.62, y=6.76, z=-54.97], ts['Slime'/1024081, l='MpServer', x=-1225.48, y=3.00, z=-103.20], ts['Slime'/1042770, l='MpServer', x=-1285.59, y=4.00, z=-94.97], ts['Slime'/1003944, l='MpServer', x=-1281.28, y=5.08, z=-8.04]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bdd.a(SourceFile:284)
	at atv.b(SourceFile:1761)
	at atv.d(SourceFile:633)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Windows Vista (x86) version 6.0
	Java Version: 1.7.0_05, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 79428840 bytes (75 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 438 (24528 bytes; 0 MB) allocated, 2 (112 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.6.4
	LWJGL: 2.9.0
	OpenGL: Intel Bear Lake B GL version 1.4.0 - Build 7.15.10.1608, Intel
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 94 (5264 bytes; 0 MB) allocated, 26 (1456 bytes; 0 MB) used